The field of art to which this invention pertains is water soluble resin compositions derived from epoxy resins and polyalkylene polyols terminated with phosphoric acid monoesters and to thermosetting coating compositions useful in the coating of flexible substrates.
In view of the air pollution caused by organic solvents and to the increasing scarcity and cost of hydrocarbon solvents, there is a continuing search for new and improved coating compositions which can be dissolved or dispersed in water.
Water-borne coatings are being investigated for use in coating flexible substrates, such as paperboard and metal foil used to package frozen foods. Coatings for such use must be flexible and adherent and must be capable of withstanding heating in both conventional and microwave ovens.
Water soluble coating compositions are disclosed in U.S. Pat. No. 4,048,179. Such coating compositions are made by reacting epoxy resins with polyethylene glycols with or without added dihydric phenol at high temperatures and long reaction times.
In U.S. Pat. No. 2,990,396, polyoxyalkylene polyols are reacted with polyepoxy compounds under Friedel-Crafts catalysis to form compositions which are useful as lubricants, dispersing agents, thickeners, suspending agents, coagulating agents, surface-active agents as well as coating, textile sizing, binding, laminating and casting compositions.
U.S. Pat. No. 3,055,876 discloses a process for suspension polymerization of vinyl monomers in the presence of a suspension agent which is the reaction product of a polyethylene glycol with the diglycidyl ether of Bisphenol A. The same sort of reaction product of a polyethylene glycol and a diglycidyl ether is used as an agglomerating agent for rubber latices as described in U.S. Pat. No. 3,438,924.
In U.S. Pat. No. 3,563,943, nonionic urethane latices are described wherein the emulsifying agent is the reaction product of aromatic diepoxides with polyethylene glycols.
U.S. Pat. No. 4,197,389 discloses hardening agents for aqueous epoxy resin compositions made by reacting a polyepoxide compound with a polyalkylene polyether polyol followed by reaction with a polyamine.
In commonly assigned pending U.S. application, Ser. No. 204,101 filed Nov. 5, 1980, water dispersible coating compositions are made by reacting a low molecular weight diglycidyl ether of a dihydric phenol, additional dihydric phenol and a diglycidyl ether of a polyoxyalkylene glycol.
Phosphoric acid terminated polyepoxide resins are described in U.S. Pat. No. 4,164,487. Such compositions can be dissolved in water and used as thermosetting coating compositions.
Adducts of epoxy resins and phosphoric or phosphonic acid are described in U.S. Pat. Nos. 3,245,940; 2,732,367 and 2,541,027. Such adducts are organic solvent soluble and are not shown to be water soluble.
Organic solvent soluble coating compositions made from epoxy resins esterified with drying oil fatty acids and phosphoric acid are described in U.S. Pat. No. 2,709,690.
In U.S. Pat. No. 4,059,550, coating compositions are disclosed which are made from aqueous dispersions of polyhydroxy polyether resins and aminoplast resins catalyzed with adducts of phosphoric acid and glycidyl polyethers of polyhydric phenols.